Safety of co-administration of COVID-19 and seasonal influenza vaccines in individuals with autoimmune diseases from the Canadian National Vaccine Safety Network

The Canadian National Vaccine Safety Network conducted active safety surveillance for adverse events following COVID-19 and influenza immunizations. This analysis evaluated the association between the administration of mRNA COVID-19 vaccines, influenza vaccines, or co-administration of both, and health events that prevented daily activities, caused work absenteeism, or necessitated medical consultation among individuals with autoimmune diseases. Between September and December 2022, vaccinated and unvaccinated participants from seven provinces and territories self-reported health events within 7 days post-vaccination or over a 7-day period for unvaccinated individuals. This analysis focused on individuals self-reporting autoimmune diseases. Surveys were completed by 6,506 individuals: 1,743 received co-administered vaccines, 2,986 received COVID-19 vaccines alone, 491 received influenza vaccines alone, and 1,286 were unvaccinated. Health event rates were 9.5% for co-administration, 9.3% for COVID-19 alone, 5.9% for influenza alone, and 6.1% for unvaccinated controls. Compared to unvaccinated individuals, the risk of health events was higher for COVID-19 and influenza co-administration [adjusted relative risk (aRR): 1.89, 95% confidence interval (95% CI) 1.41-2.52], and COVID-19 alone [aRR: 1.86, 95% CI, 1.40-2.47], but not for influenza alone (aRR: 1.16, 95% CI, 0.76-1.78). No significant change in emergency department visits or hospitalizations was observed in any vaccine group compared to unvaccinated controls. In individuals with autoimmune diseases, mRNA COVID-19 vaccination increases mild to moderate health events compared to unvaccinated individuals. However, the rate of these events was similar when COVID-19 vaccines were administered alone or concomitantly with influenza vaccines, indicating no additional risk associated with co-administration.